No, the same happens when you pay at a restaurant or check into a hotel. The merchant reserves an amount of credit adequate to cover the maximum likely charge. If you travel extensively this can tie up a substantial portion of your credit line. This is one of the original points of difference between charge cards (e.g. American Express and Diners Club) and bank cards (e.g. Master Charge and BankAmericard), but these days MasterCard World and VISA Signature cards have the same "no present spending limit" feature which renders the hold harmless to most people.